1. Scope of the Invention
This invention relates to the dealkoxyhydroxymethylation of aldehyde acetals. More particularly, it relates to a novel process for the dealkoxyhydroxymethylation of certain dialkyl-, dicycloalkyl-, diaryl-, or cyclic-aldehyde acetals by reacting said acetals with syngas, i.e., hydrogen and carbon monoxide, in the presence of novel ruthenium carbonyl-cobalt carbonyl catalysts to form the corresponding glycol monoethers. Still more particularly, it relates to the catalysts per se and methods for preparing the same. The acetals described herein may be prepared separately or formed in situ from the corresponding aldehyde and alcohol precursors.
The glycol ethers described herein encompass known classes of compounds having various uses, as for example as jet fuel additives, cleaners, coatings solvents, intermediates in the production of certain diphthalates, and the like.
2. Description of the Prior Art
One current well-known method of manufacturing ethylene glycol monoethers such as monoalkyl ethers consists of reacting ethylene oxide with the alcohol corresponding to the desired alkyl ether, employing various known catalyst systems.
Alternatively, the cobalt-catalyzed reaction of aldehydes or their dialkyl acetals with syngas, i.e., a carbon monoxide-hydrogen mixture, to form the corresponding glycol ether is also described in the art. Thus, for example, a method of making ethylene glycol ethers is described in U.S. Pat. No. 2,525,793 which employs cobalt oxide to catalyze the reaction of methylal with syngas to provide a reaction mixture which, after hydrogenation over nickel, gives relatively uneconomical conversions on the order of 25-33%.
Numerous attempts have been made to obtain more practical yields of glycol ethers from aldehydes or their dialkylacetals. A number of promoters have been used in conjunction with various cobalt catalysts in an effort to improve reaction rates and product yields. U.S. Pat. No. 4,062,898, for example, discloses a ruthenium chloride-promoted cobalt iodide catalyst which hydrocarbonylates formaldehyde dimethylacetal (methylal) to ethylene glycol monomethyl ether, (EGMME) in yields of 10% or less. The reaction temperature required is 185.degree. at 20 atm. or above. A second method, described in Jpn. Kokai Tokkyo Koho 81 83,432, (1981) uses substantial quantities of 2,4,6-collidine or similar aromatic amines to promote the cobalt carbonyl-catalyzed hydrocarbonylation of methylal in benzene as a solvent. The reaction of methylal with highly pressurized syngas in this process at 190.degree. C. for 10 hours gave 44% selectively to EGMME at 98% conversion. A further patent, Euro. Pat. Appln. EP 34,374. (1981) uses both iodine and triphenyl or tricyclohexylphosphine together with RuCl.sub.3.H.sub.2 O to promote the Co(OAc).sub.2.4H.sub.2 O--catalyzed hydrocarbonylation of methylal using 3000 psig of syngas, and temperatures of between 150.degree. and 175.degree. C. to obtain results nearly comparable to those of the Japanese.
More recently, Knifton has found that cobalt carbonyl promoted with a Group VIB donor ligand catalyzes the hydrocarbonylation of an aldehyde in an alcohol to make ethylene glycol monoethers; U.S. Pat. No. 4,308,403. Yields of ethylene glycol monobutyl ether (EGMBE) as high as 61 wt.% were reported in this patent. A cyclopentadienyl-ligated cobalt catalyst is also effective for these reactions giving glycol ethers in up to 54% yield; U.S. Pat. No. 4,317,943.
Propylene glycol monoalkylethers are formed by contacting high pressure mixtures of carbon monoxide and hydrogen with either an acetal or an aldehyde and an alcohol using a cobalt catalyst promoted with a tin- or germanium-containing compound; U.S. Pat. No. 4,356,327. Yields of glycol ethers up to 31 wt.% were reported in this patent. Ethylene glycol ethers were also formed from a formaldehyde acetal or formaldehyde and an alcohol using tin or germanium promoters for cobalt carbonyl; U.S. Pat. No. 4,357,477. The highest glycol ether yield (EGMBE) was 53% in this case.
Finally, propylene glycol monoalkyl ethers were formed by hydrocarbonylation of acetaldehyde acetals or acetaldehyde and alcohols using rhodium, ruthenium or nickel compounds to promote either cobalt carbonyls or cobalt compounds having group V ligand systems attached. Glycol ether yields up to 28 wt.% were realized when these promoters were used; Knifton, U.S. Pat. No. 4,390,734 (1983).
Thus, the use of various promoters for the cobalt-catalyzed hydrocarbonylation of aldehydes or acetals has resulted in glycol ether yields of from 10-61 wt.%, depending on the glycol ether produced. The highest reported yields of EGMME is 44%, of EGMBE is 61% and PGMEE is 28%.